Labile pyrogenic dissolved organic carbon in major Siberian Arctic rivers: Implications for wildfire-stream metabolic linkages

Biomass burning produces a spectrum of thermally altered materials that releases pyrogenic carbon (PyC) to terrestrial, atmospheric, and aquatic systems. Most studies focus on the refractory end of the PyC spectrum, derived from middle- to high-temperature combustion. Low-temperature PyC is produced during wildfires and has been found to be particularly labile and water soluble. Here we find that in each of the major Siberian watersheds, low-temperature fire-derived biomarkers are present in detectable concentrations during all flow regimes of the 2004-2006 sampling period, confirming that PyC is an intrinsic component of the dissolved organic carbon (DOC) pool mobilized by hydrologic events. Gymnosperm combustion, from the southern portions of these watersheds, is the primary source of this Py-DOC input. Using first-order degradation rates and transit times of water through these rivers, about half of the total estimated flux of this material may be remineralized during transport from fire source to river mouth (20-40days), demonstrating the input of a labile source of PyC to these watersheds.